I thought the Crusaders destroyed countless priceless literary treasures when they sacked the city in 1204. Given that the Byzantines were supposed to been extremely culturally active from the restoration of 1261 to 1453 I suppose it is possible that many more literary creations were created and destroyed. The Turks were pretty determined to destroy anything which might have been a rallying point for restoring the Byzantine Empire (actually the sultans considered themselves the Byzantine Emperor) but I have never read that the destruction reached systematic levels.